Recording materials based on color-forming reaction of a coloring chromogen and a developer have been widely used for thermal recording papers to be utilized for output recording by facsimile, printers, etc., or for carbonless papers to be utilized for accounting cards for producing several copies at once, since those recording materials enable to make recording in short time by using relatively simple apparatuses without requiring complex recording procedure, such as developing, fixing, etc.
For such a recording material, the one which can develop color immediately, prevent color change in non-image area (hereinafter referred to as background) and provide high preservability to colored-images and background, have been required. Further, in recent years, such recording materials have been used in a great amount especially in the field of label printing where reliability to recorded-images being highly respected. In addition, recording materials that can provide colored-images having high preservability and resistance against plasticizers and oils, which are contained in organic high molecular materials being used for packages, have been strongly required. For such purpose, investigation from various points of view to find efficient auxiliary agents such as stabilizers as well as color-forming chromogens and color developers have been carried out. However, such materials having sufficient properties as described above have not been found yet.
For the examples of compounds similar to the compound specified in the present invention, various diphenyl sulfone derivatives, phenethyl alcohol derivatives and the like can be exemplified. These compounds are known as a color developer to be used for recording materials. Diphenyl sulfone derivatives having either alkoxyl or aralkyloxyl group at one side and hydroxyl group at the other side are disclosed in Japanese patent laid-opened Nos. Sho 57-210886, Sho 58-20493, Sho 58-82788, Sho 58-132593, Sho 60-13852, World opened No. WO84/02882, etc. respectively.
More recently, some patent applications for aiming at improving the preservability of recording materials as described above have disclosed recording materials containing epoxyl group, such as novolac-type epoxy resins and glycidyl compounds. The applicant of the present invention has also filed a patent wherein a compound of 4-hydroxy-4'-(2-methylglycidyloxy)diphenyl sulfone is specified for the same object. However, all of those compounds have not been capable of providing enough preservability to developed-images.
Furthermore, the applicant of the present invention has disclosed a compound represented by the following general formula as an image-stabilizing agent in Japanese patent laid-opened No. Hei 5-194368. ##STR3##
However, the compound mentioned hereinabove has been found as having inferior property in resistance to moisture and heat, and it can give only less density to developed-color and less sensitivity, when it is used as a color developer.
As described above, in recent years, the improvement in recording materials for aiming at securing preservability for colored-images, especially resistance to plasticizers and oils, are highly required. Therefore, it is an object of the present invention to provide recording materials which can give excellent preservability for colored-images, enough color density when it is developed, and excellent property for preventing color change in the background.